Electrocatalytic CO2 Reduction with Re-Based Spiro Bipyridine Complexes: Effects of the Local Proton in the Second Coordination Sphere†

Main observation and conclusion We report herein a Re-based tricarbonyl catalyst [fac-Re(L1)(CO)(3)Cl] (Re1) bearing a spiro center and a phenol group as a local proton source in the second coordination sphere. Due to the large steric spiro group, dimerization of one-electron reduced species was completely eliminated, improving the stability of Re1. Simultaneously, the phenol group in the second coordination sphere improves the formation of an H-bonding chain that promotes the protonation of CO2 reduction intermediates, boosting the electrocatalytic CO2 reduction activity of Re1. Mechanistic studies reveal that the doubly reduced complex Re1b is active for CO2 addition.

Automated summary

In this study, a Re-based tricarbonyl catalyst Re1 with a spiro center and a phenol group was reported, which showed improved stability due to the large steric spiro group. The phenol group in the second coordination sphere promoted the protonation of CO2 reduction intermediates, enhancing the electrocatalytic CO2 reduction activity of Re1. Mechanistic studies revealed that the doubly reduced complex Re1b was active for CO2 addition.